Bearings for rotatably supporting the ends or mid-portions of drive shafts and other types of shafts have been used for many years. Such bearings are available in a wide variety of forms for use under an equally wide variety of conditions. For example, bushings made of Teflon® or other low friction plastic material are often used in situations where the shafts supported by the bearings are to be driven at relatively low rotation rates and/or are to bear relatively low lateral loads. To accommodate higher rotation rates and loads, bushings made of relatively soft porous metal such as bronze are often used. These types of metal bushings are advantageous over plastic bushings because they are able to bear higher lateral loads imparted by shafts and are able to accommodate higher rotation rates without overheating. In addition, porous metal bushings can be impregnated with oil or another lubricant to reduce their coefficients of friction substantially.
In situations where high rotation rates and/or high lateral loads are to be accommodated, rolling bearings such as roller bearings, needle bearings, and ball bearings may be preferred. Rolling bearings offer high lateral load bearing capability and have low frictional resistance to accommodate higher rotation rates than static bushings. In addition, miniature rolling bearings often are preferred for use in precision equipment such as printers, copy machines, and the like because of their low friction and high reliability.
When rotating drive shafts are used in equipment such as, for example, printers, plotters, and photocopy machines, it is common to support the shafts in bearings that are mounted in facing walls of a relatively thin metal chassis. In these circumstances, the bearings must be mounted to the walls of the chassis in such a way that they are precisely aligned with each other to receive the shaft without binding. In the past, this has been accomplished in a variety of ways. In some instances, opposing walls of the chassis are punched to form aligned holes. The bushings or bearings are then press fit into a mounting collar having mounting dogs or tabs for mounting the collar to a wall of the chassis with rivets or bolts to align the bearings with each other and with the punched holes in the chassis. While this method can work well, it is nevertheless relatively expensive because the mounting holes for the collars must be very precisely positioned and the collars must be precisely machined for properly aligning the bearings. In addition, several precision machining steps are required to mount the bearings to the walls properly.
This situation has been addressed for roller and needle bearings in U.S. Pat. No. 5,911,515 entitled Self Clinching Rolling Bearing Assembly and for static bushing-type bearings in U.S. Pat. No. 6,238,096 entitled Press-Alignable Bearing Assembly (both owned by the assignee of the present disclosure). The disclosures of these patents are hereby incorporated by reference in their entireties. Generally, these patents disclose self-alignment mechanisms for static and roller bearings that include bearing sleeves with spherical outer surfaces that allow the sleeves to move within their retainers, which are specially shaped to receive and retain the sleeves. While effective, this entails additional manufacturing steps and precision that can increase cost.
In some instances, needle and roller bearings and static bushings are not the most desirable option and a ball bearing is the best choice. For example, ball bearings tend to have a significantly lower profile than roller bearings and bushings and so may be desirable where space is limited. Further, the use of a ball bearing allows a non-hardened shaft to be journaled in the inner sleeve of the ball bearing because the shaft itself does not ride on the balls of the bearing as is does with roller bearings. Ball bearings also can be sealed and permanently lubricated and generally accommodate much higher rotation rates that roller bearings and bushings. They also are preferred for use in higher precision equipment such as medical and research instruments. Unfortunately, however, ball bearings that are either self-clinching or press-fittable as well as self-aligning such as the roller bearings and bushings disclosed in the above patents have not been available, especially for small diameter shafts under about 0.5 inches (12 mm) in diameter. There is thus a need for such a ball bearing.
Self-Aligning Ball Bearings and miniature ball bearings have been available for many years in a pre-mounted form where the bearings are permanently contained within cast iron pillar blocks having mounting flanges that are secured to a surface with fasteners such as rivets or bolts. However, a miniature press-fit self-aligning ball bearing assembly that can selectively be installed in a stock pillar block or stock mounting flange as well as being pressed into a thin sheet material has been an elusive goal. Further, pre-mounted ball bearings can be less economical and their installation can be labor and material intensive and require higher precision. A need exists for a ball bearing, and especially a miniature ball bearing, that addresses the above mentioned and other issues.
It is to the provision of a ball bearing, and particularly a self-clinching or press-fitting miniature ball bearing, that is self-aligning and that addresses the above and other needs that the present disclosure is primarily directed.